(1) Field of the Invention
The present invention relates to a sun visor for an automobile having a sound absorbing structure, and a sound absorbing structure for an automobile in which an interior base material is provided on the cabin side of a body panel.
(2) Description of Related Art
Typically, the body of an automobile is constituted by a plurality of panels which are press-molded and welded to form the outer shape of the automobile and various interior spaces such as a passenger cabin, an engine compartment, a luggage compartment, and so on. The body is basically formed by partially welding a panel on the vehicle exterior, known as an outer panel, and a panel on the vehicle interior, known as an inner panel, such that a space remains therebetween. The formed body is submerged in a rustproofing liquid to form an undercoating, subjected to drying processing in a furnace, and then finished by applying a coating thereto a plurality of times. Various functional components are then attached to the body, and various interior materials are carpeted so as to cover the inner panel on the cabin interior side of the body. The interior material is typically formed by covering a thick base material made of a thermoplastic resin having excellent thermal moldability with a designed surface material. An interior base material is molded into a three-dimensional shape corresponding to the shape of the inner panel in a carpeting position, carpeted onto the inner panel, and engaged with the inner panel using an engagement tool such as a resin clip.
Further, a light-shielding sun visor is installed in the passenger cabin of the automobile for preventing glare on the eyes of a passenger caused by direct sunlight or the lights of an opposing vehicle. In this type of sun visor, a plate-form core material is covered with a surface material such as fabric or leather to enhance the design quality thereof. An L-shaped spindle is fixed in a position near the front window on the ceiling of the automobile cabin, and one side edge of the sun visor is inserted into the spindle so as to be supported rotatably. The passenger sets the sun visor in a horizontal state when not in use so that the sun visor is stored in a storage position parallel with the ceiling of the vehicle. To block sunlight or the like coming from the direction of the windshield, the sun visor can be rotated about a horizontal central axis in the direction of the front window, and to block sunlight or the like coming from the side window, the sun visor can be rotated further about a vertical central axis in the direction of the side window. By having the passenger rotate the sun visor manually while holding a part of the sun visor by hand in this manner, the sun visor can be positioned freely and used in the position in which it is disposed.
The sun visor described above must possess a certain degree of rigidity to ensure that it does not bend or become deformed when the passenger applies force thereto in order to perform a rotation operation. Accordingly, a sun visor main body (sun visor core) employs a plate-form core material having a constant rigidity such as a wooden board, a thermoplastic resin molded body, or a resin particle foam-molded body. Further, the core material is covered in a surface material made of various types of fabric or leather to provide the sun visor with a design quality suited to the interior material of the passenger cabin.
FIG. 7 shows a cross-section of an automobile sun visor 900 disclosed in Japanese Utility Model Publication H6-845. In this sun visor 900, a frame 904 is formed in advance by bending a metal wire made of steel wire or the like into the desired outer peripheral shape of the sun visor. A plate-form core material 902 made of comparatively rigid cardboard or the like is fitted into the frame 904 and fixed with tape, for example. The integrally-formed frame and reinforcing plate are sandwiched on both sides by a padding material 906 made of slab urethane or the like and serving as a cushioning layer. A surface layer 908 knitted into a bag form having an interior space corresponding to the core material 902 is provided on the outside of the padding material 906.
As described above, a space is provided between the outer panel and inner panel of the body of the automobile, and hence many locations are formed to be hollow. Since these locations are basically cavities, various noises such as road noise, engine noise, and wind roar generated as the automobile travels along a road propagate through the cavities and leak through the inner panel into the passenger cabin in which the passengers are seated, or reach the passenger cabin through the luggage compartment, engine compartment, and so on adjacent to the passenger cabin, thereby impeding passenger comfort. To make the passenger cabin quieter, various proposals have been made for securing sound absorbency and sound insulation in the carpeting material for carpeting the cabin interior side.
In Japanese Unexamined Patent Application Publication H6-286530, a pillar garnish made of a synthetic resin and having a hollow portion formed into a surface-shape is used, and sound insulation is achieved by means of the hollow portion, which is a completely closed space.
In Japanese Examined Patent Application Publication 2000-516175, sound insulation is achieved by fixing a noise-reducing assembly package comprising a hard layer having minute pores to a flat, surface-shaped body part.
Japanese Unexamined Patent Application Publication 2004-90829 describes a sun visor comprising a plate-form core material having a constant rigidity and a constant air permeability, and a surface material having a constant air permeability which is disposed so as to cover the surface of the plate-form core material.
With the technique of Japanese Utility Model Publication H6-845, infiltrating sound such as road noise infiltrating the cabin interior is reflected by the sun visor and enters the ears of the passenger, and hence it is assumed that infiltrating sound which infiltrates the cabin interior is not reduced.
With the technique of Japanese Unexamined Patent Application Publication H6-286530, infiltrating sound is reflected on the cabin side surface of the pillar garnish and enters the ears of the passenger, and hence it is assumed that infiltrating sound which infiltrates the cabin interior is not reduced.
In the technique of Japanese Examined Patent Application Publication 2000-516175, the noise-reducing assembly package must be fixed to the surface-shaped body part, and therefore, in order to achieve a favorable design quality, the assembly package must be fixed to the entire surface of the cabin interior. Therefore, the material cost of the assembly package is high, and the operation to install the assembly package takes time, leading to an increase in the cost of the operation. Accordingly, there is room for improvement in terms of cost reduction.
With the technique of Japanese Unexamined Patent Application Publication 2004-90829, infiltrating sound entering the ears of the passenger is reduced to a certain extent. However, it is desirable to reduce the infiltrating sound which enters the ears of the passenger even further.
Note that the technique described in Japanese Unexamined Patent Application Publication 2002-356184 refers to a working vehicle rather than an automobile, and therefore cannot be applied to the present invention. As shown in FIG. 4 of Japanese Unexamined Patent Application Publication 2002-356184, in this document a sound absorbing sheet is formed by laying a sound absorbing material on the underside of a step mat having a large number of holes punched therein, and a silencing effect is obtained by carpeting or affixing the sound absorbing sheet onto parts of the cabin interior excluding the window portions. However, since the sound absorbing sheet is provided on all surfaces of the cabin interior excluding the window portions, the material cost of the sound absorbing sheet is high, and the operation to install the sound absorbing sheet takes time, leading to an increase in the cost of the operation. Accordingly, there is room for improvement in terms of cost reduction.
Furthermore, in Japanese Unexamined Patent Application Publication 2002-356184, a resonance chamber requiring a space portion which is independent from the cabin interior is provided in the ceiling wall portion of the cabin interior of the working vehicle, and a silencing effect is obtained by providing a pipe from the resonance chamber to the cabin interior such that the resonance frequency component of the engine noise which diffuses through the cabin interior is reduced through attenuation by frictional resistance with the periphery thereof As shown in FIGS. 9 to 12 of the document, however, the resonance chamber is attached to the ceiling wall portion as a downwardly-protruding separate member, and hence there is particular room for improvement in terms of design and safety with respect to an automobile for traveling at high speed.